Operation in very close coupling of an electromagnetic transponder system

  • US 6,703,921 B1
  • Filed: 04/05/2000
  • Issued: 03/09/2004
  • Est. Priority Date: 04/07/1999
  • Status: Expired due to Term
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First Claim
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1. A method of data transmission between a terminal for generating an electromagnetic field and a transponder, the terminal and the transponder each including an oscillating circuit forming an antenna, and said transponder including an electronic circuit adapted to drain and give back power provided by the electromagnetic field from the terminal, the oscillating circuits of the transponder and of the terminal being capable of transmitting radio-electric signals of determined frequency, the method including causing a detuning of at least one of the oscillating circuits with respect to the determined frequency, so as to decrease a coupling coefficient between the oscillating circuits while maintaining communication between the transponder and the terminal, when the transponder and the terminal are very close to each other.

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